Colour formers

ABSTRACT

Colourless colour formers which are compounds characterised by the general formula:   WHEREIN R1, R2 and R3 each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R4 represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyano or sulphamyl radical; n represents an integer of from 0 to 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs of ortho positions; Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula -NR6- wherein R6 denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a five-or six-membered ring is formed with Y, -NR3- and A.

United States Patent 11 1 Hughes et al.

[ COLOUR FORMERS [75] Inventors: Nigel Hughes; Andrew Hunter Morris Renfrew, both of Blackley, Manchester, England [73] Assigneez Wiggins Teape Limited, London,

England 22 Filed: Feb. 16, 1973 21 Appl. No.: 333,347

[30] Foreign Application Priority Data Feb. 21, 1972 Great Britain 7848/72 [52] U.S. Cl. 117/36.2, 117/368, 260/279 R, 260/335 [51] Int. Cl B4lm 5/22 [58] Field of Search 117/362, 3618; 260/335, 260/279 R [56] References Cited UNITED STATES PATENTS 3,501,331 3/1970 Kimura et al. 260/335 3,540,912 11/1970 Lim 117/362 3,649,649 3/1972 Orita et a1 260/335 3,725,416 4/1973 Yamamoto 1 117/362 3,746,562 7/1973 Lin 117/362 Primary Examiner-Michael Sofocleous Attorney, Agent, or Firm-Burns, Doane, Swecker & Mathis [57] ABSTRACT Colourless colour formers which are compounds cha- Sept. 24, 1974 racterised by the general formula:

wherein R, R and R each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyano or sulphamyl radical; n represents an integer of from 0 t0 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs of ortho positions, Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula NR wherein R denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a five-or six-membered ringis formed with Y,

6 Claims, No Drawings COLOUR FORMERS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to colour formers and more particularly to coulourless colour formers suitable for use in pressure-sensitive copying systems.

2. Description of the Prior Art In known pressure-sensitive copying systems a colourless colour former, dissolved in a suitable solvent, is brought into contact with an electron-accepting substance whereupon a coloured image in the parent dyestuff is formed.

In one known system a sheet of pressure-sensitive copying paper comprising a paper base carrying the colour former in encapsulated form is placed in contact with a copy sheet comprising a paper base having an active mineral surface coating, for example a surface coating of a so-called acid clay. When local pressure is applied to the sheets by means of, for example, handwriting or typewriting, the capsules on the pressed portions are broken and the colour former comes into contact with the active mineral on the copy sheet and a coloured image of the original wrting is formed on the copy sheet.

Various colour formers for use in such systems are known, but a difficulty has always been that if a dark image, for example a black image, is required then a combination of different colour formers has been required. The use of combinations of colour formers can lead to difficulties in production and also difficulties in providing a copy sheet having an active surface able to react as necessary with the colour formers used.

Clearly it would be desirable to use a single colour former to provide a dark, for example a black image.

SUMMARY OF THE INVENTION According to the invention there are provided colourless colour formers which. are compounds of the general formula:-

wherein R" R and each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyuno or sulphamyl radical; n represents an integer of from to 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs ofortho positions; Y represents a direct link, optionally substituted methylene, o xygen, sulphur or a group of the formula NR wherein R denotes hydrogen or an o tionally substituted alkyl. aryl or aralkyl radical;

and Z represents an optionally substituted divalent organic radical such that a fiveor six-membered ring is formed with Y, N R and A.

Alkyl radicals which may be represented by R and R include methyl and preferably ethyl. When R or R forms part of a heterocyclic ring containing the attached nitrogen atom this may be because R and R are joined together to form a divalent chain of atoms which together with the attached nitrogen atom constitutes a heterocyclic ring such as a pyrrolidine or morpholine ring.

A is preferably a benzene ring having points of attachment in the l, 2, and 4, 5 positions. Z may be a 1,2- phenylene radical.

The colour formers of the invention may be prepared by reacting a compound of the formula:

COOH

wherein R, R R and n have the significances already stated, with a compound of the formula:

whereinA, Y, Z and R have the significances already stated and R represents hydrogen or lower slkyl, the reaction being performed in the presence of a suitable condensing agent, preferably sulphuric acie or polyphosphoric acid.

The colour formers of the invention provide darker images than the colour formers which have generally been used to date, including black images in some cases, when reacted with a suitable electron-accepting substance. Such substances include silica and attapulgite, which is a so-called acid clay, and synthetic resins containing unreacted phenolic hydroxyl groups.

DETAILED DESCRIPTION The invention is illustrated but not limited by the following Examples in which all parts and percentages are by weight.

EXAMPLE 1 31.3 parts of 4-diethylamino-2-hydroxybenzoyl-obenzoic acid, 21.1 parts of 2-methoxyacidan and I00 parts of 98 percent sulphuric acid are heated at 100C with stirring for 2 hours than cooled. The reaction mixture is drowned into water and the solid which separates is filtered off and then slurred in an excess of 2N ammonium hydroxide solution to give an off-white solid. Filtration and drying gives the product, 39 parts.

A toluene soltuion of the product which has the structure gives a dark-coloured image on contact with a so-called acid clay.

EXAMPLE 2 6.23 Parts of o-(4-diethylamino-2-hydroxy)benzoyl benzoic acid, 4.87 parts of 2-methoxy-9-chloroacridine and 50 parts of polyphosphoric acid are heated at 100C with stirring for 6 hours then cooled. The reaction mixture is drowned into ice and the suspension made alkaline with ammonia. The solid which separates is collected, washed well with water and dried to give 4.7 parts of the product of structure:

A toluene solution of the above fluoran gives a dark blue image on contact with electron accepting surfaces.

EXAMPLE 4 3.1 1 Parts of o-(4-pyrrolidin-l-yl-2-hydroxy)benzoyl benzoic acid, 2.01 parts of 3-methoxy-5,6,7,8- tetrahydrocarbazole and 30 parts of sulphuric acid are heated at 80C for 6' hours then cooled. The reaction mixture is drowned into water and made alkaline with ammonia. The solid which is formed is collected,

washed with water and dried to .give 2.3 parts of the product of structure:

i 4 a Y 0 U i (W T O /K A toluene solution of the above colour former gives a dark red image on contact with electron accepting surfaces.

EXAMPLE 5 4.51 Parts of o-(4-diethylamino-2-hydroxy)benzoyl-3 ',4',5.6-tetrachlorobenzoic acid, 1.97 parts of 3-methoxycarbazole and 30 parts of sulphuric acid are heated at 100C for 6 hours then cooled. The reaction mixture is drowned into water and made alkaline with ammonia. The solid which is formed is collected, Washed with water and dried to give 1.8 parts of the product of structure:

A toluene solution of the above colour former gives a dark bluish-red image on contact with electron accepting surfaces.

EXAMPLE 6 6.26 pagts ofol 4-diethy lamino-2-hydroxy benzoyl) benzoic acid, 494 parts of I-ethyI-Z-rnethyl-methyl- 3-carboethoxy-5-hydroxy indole and 22 parts of 98 percent sulphuric acid are heated at 75C for 12 hours. The reaction mixture is drowned into water and the precipitated tar is extracted into chloroform. After drying over magnesium sulphate, the chloroform solution is evaporated to dryness and the residue is recrystallised from petroleum ether.

3.3 parts of a white solid melting at 218C and having the ada s;

are obtained. A toluene solution of the above colour former gives a dark ruby-red colour on contact with electron accepting surfaces.

EXAMPLE 7 The preparation of Example 6 is repeated except that the reaction temperature is O5C. 9.3 parts of a white solid. melting point 253C and having the structure:

are obtained. A toluene solution of the above colour former gives a scarlet colour on contact with electron accepting surfaces EXAMPLE 8 In place of the 4.94 parts of l-ethyl-2-methyl-3- carboethoxy-5-hydroxy indole used in example 6 there are used 5.94 parts of l-ethyl-2-methyl-3-' carboethoxy-5-hydroxy-6,7 benz indole. 4.3 parts of a product having the structure:

02115 ZNU is obtained K toluene solution of this colour former gives a dark ruby-red colour on electron accepting surfaces.

III-C1115 EXAMPLE 9 In place of the 6.26 parts of o-(4-diethylamino-2- hydroxy benaoyvbenzoic acid usedin Example 6 there are used 6.22 parts of o-[4-(pyrrolidin-l-yl)-2- hydroxybenzoyl1benzoic acid. 3.5 parts of a white solid having melting point 232C and the structure:

j l ll are obtained. A toluene solution of the colour former gives a dark ruby-red colour on electron accepting surfaces.

EXAMPLE 10 6.26 parts of o-(4-diethylamino-2-hydroxybenzoyl)- benzoic acid, 3.3 parts of l-methyl-6-hydroxy py-tetrahydroquenoline and 22 parts of 98 percent sulphuric acid are heated at 50-55C for 12 hours. The reaction mixture is drowned into water and neutralised by addi- 6 tion of concentrated ammonia hydroxide solution. The white precipitate is collected by filtration, washed with water and recrystallised from n-propanol. 7.3 parts of a white solid having the structure:

6 zHs) 2NO EH3 are obtained. A toluene solution of the colour former gives a green colour on electron accepting surfaces.

EXAMPLE 1 1 In place of the o-(4-diethylamino-2-hydroxybenzoyl) benzoic acid used in Example 10 there are used 6.54 parts of o-[ 4-( morpholinl -yl )-2-hydroxybenzoyl benzoic acid. The product which has the structure:

trips I is obtained as a white solid. A toluene solution gives a greenish-black colour on electron accepting surfaces.

We claim:

1. A pressure sensitive copying paper comprising a paper base carrying in encapsulated form a colour former of the general formula matic ring the points of attachment being at two pairs of ortho positions; Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula l lR wherein R denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a fiveor six-membered ring is formed with Y, NR and A.

5. The copying paper of claim 1 wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur.

6. The copying paper of claim 1 wherein n is 0 and wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur. 

2. In combination, a pressure-sensitive copying paper as claimed in claim 1 and a copy sheet comprising a paper base having an active mineral surface coating capable of reacting with the colour former to provide a coloured image.
 3. The copying paper of claim 1 wherein n is
 0. 4. The copying paper of claim 1 wherein R4 is chloro.
 5. The copying paper of claim 1 wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur.
 6. The copying paper of claim 1 wherein n is 0 and wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur. 